The appointment was approved earlier this month (7 October) by the Advisory Committee on Business Appointments (ACOBA), and the letter confirming this was published today. The project will "involve several days’ work", the letter said.
Swinson was the Liberal Democrat MP for East Dunbartonshire between 2005 and 2015, and held four different roles in the departments of education, business and culture, media and sport from 2012 onwards, during the coalition government.
Portland’s chief operating officer Alexandra Farley said: "Attracting and nurturing top talent is at the core of our business. As part of that, we want Portland to set the standard when it comes to diversity.
"We are delighted to be working with Jo Swinson, an acknowledged expert in the area, to gain an outside perspective and fresh ideas on how we can make Portland the best possible workplace".
According to LinkedIn, Swinson currently runs Equal Power Consulting, which "helps businesses identify and deliver organisational change to enable both women and men to thrive", and other work she has taken on since leaving parliament, ACOBA approval letters show, include positions with the ASA, CIPD and CMI.
Parliament's Public Administration and Constitutional Affairs Committee is currently running an inquiry into ACOBA's role - it is seen as toothless by some detractors, as it holds no enforcement powers.
Omnicom-owned Portland, one of the UK's largest PR firms, is to open an office in Singapore in the near future, PRWeek reported on Friday.